Retrovenous diastolic myocardial perfusion (RVDP) with oxygenated blood via the coronary sinus and coronary veins has been shown experimentally to provide 45% of the normal coronary blood flow. RVDP therapy could significantly alter the morbidity of patients with coronary artery disease and acute myocardial ischemia. Current experimental RVDP catheters require a second arterial source of oxygenated blood and abnormally elevate venous pressures. Single, triple lumen RVDP catheters will be fabricated and bench tested with roller pump, pulse chamber, membrane oxygenator and control module. Safe boundary conditions of RVDP pressure and flow will then be evaluated by acute experiments in three normal sheep for feasibility and to determine if mean coronary sinus and venous pressures can be reduced with active coronary venous decompression. RVDP will then be applied in three normal sheep for 6 hours to test for any myocardial or vein damage. RVDP will also be applied in three sheep 1/2 hour after coronary artery ligation to determine percent salvage of injured myocardium "at risk". RVDP will have a significant therapeutic and commercial impact on the treatment of myocardial ischemia and cardiogenic shock, as a drug delivery system (e.g. streptokinase, cardioplegia) and as a routine therapy for patients undergoing percutaneous transluminal angioplasty, cardiac diagnostic procedures or intra-aortic balloon pumping.